An increase in web surfers, requests for quality of service (QoS) and service availability has led to an increased demand for transmitting a packet of information from a source host to a destination host. For such purposes the multi protocol label switching (MPLS) has become the standard in internet engineering. The multi protocol field switching (MPLS) is a signaling protocol for exchanging label information generated from routing information and defines a process for generating and deleting a label and for passing a pre-determined packet through a traffic-engineering path by allocating traffic information for traffic engineering and explicit path information to a label.
Multi protocol label switching (MPLS) simplifies forwarding functions and provides traffic-engineering functions for improving transmission speed and quality of service (QoS) and for responding to data the multi protocol label switching (MPLS) is widely applied in the surroundings of high-speed switching networks such as asynchronous transfer mode (ATM) switching networks or frame relay networks.
A traffic engineering scheduling device for multi protocol label switching (MPLS) is disclosed in a United States Patent Application Publication of Song (US 2003/0137983). As disclosed therein, the device comprises a traffic-engineering profile module for receiving and processing subscriber information including a traffic-engineering path. Information relating to the traffic-engineering path, a traffic-engineering scheduling module, a time attributed property for generating/modifying/deleting the traffic-engineering path and making the traffic-engineering profile module generate/modify/delete the traffic-engineering path. The module also includes a signaling protocol control module controlling a signaling protocol for constructing a routing path, and performing generation/modification/deletion of the traffic-engineering path according to request of the traffic-engineering profile module. Therefore, it is possible to develop a communication product or data service changing dynamically the service quality or contents depending on time. As a result various types of communications products can be developed and various services can be supplied to subscribers. The telecommunications carrier can maximize efficiency in the network in itself, and even in the marketing fields for the network.
A method for sending data packets through a multi protocol label switching (MPLS) network and a MPLS network is disclosed in a Patent Publication (US 2003/0053464 of Chen et al. As disclosed therein a method of sending data packets to a multi protocol label switching (MPLS) network is provided. It comprises assigning to each packet a quality of service (QoS) class flag, then routing each packet through the MPLS network depending on the QoS class flag assigned.
A U.S. Pat. No. (6,314,095) of Loa discloses a method and apparatus for a high-speed multi media content switch with compressed internet protocol (IP) header. An IP packet is retrieved having a header and a payload. The header of the IP packet is compressed. The payload is appended to the compressed header to create a compressed IP packet. A multi protocol label switch (MPLS) virtual circuit is established through a plurality of IP routers terminating at a destination of the IP packet. The compressed IP packet is converted into a MPLS packet. The MPLS packet is transmitted through the MPLS virtual circuit. The MPLS packet is reconverted into the compressed IP packet at the destination. The compressed IP packet is compressed at the destination.
Compression techniques essentially reduce the size of data to be delivered and hence reduce the amount of bandwidth required to deliver this content. Standard compression techniques such as Motion Picture Expert Group—MPEG Standard provide Discrete Cosine Transform (DCT) based lossy compression. Playback of compressed video using DCT does not tolerate losses of parts of the compressed frames due to network congestion and quality of playback becomes unacceptable.
Wavelet based techniques provide an alternative compression methodology. These techniques are non-standard but can provide graceful degradation when parts of compressed data frames are dropped due to congestion. Such techniques can identify parts of the compressed frames that can be dropped under congestion without appreciable loss of quality.
The difference between DCT and Discrete Wavelet Transform (DWT) is that in the wavelet transform, the process is performed on the entire image and the result is a hierarchal representation of the image, where each layer is a frequency band. Using DWT techniques, some of the high frequency contents can be dropped with minutely perceptible degradation of decompressed image quality. In the worst case, low frequency bands of compressed images can help restore a coarse grain representation of an original image. Due to this characteristic, graceful degradation of image quality using DWT based compressed data is an ideal candidate to test load shedding based congestion control schemes.
The idea of Embedded Image Coding using Zerotrees of Wavelet Coefficients (EZW) was presented by Shapiro. The EZW coder exploits the above mentioned characteristic of DWT technique. It applies wavelet transformation and heuristics such that the encoded data is ordered in terms of visual significance. The encoded data is disseminated as an embedded bit-stream with the data in descending order of significance. The degradation of visual quality, as a result of not sending data of low-significance, can be managed so that the resulting decoded image is still useable by the user and the application.
MPLS is a layer 3 switching technology that emphasizes the improvement of packet forwarding performance of backbone routers. The main idea behind MPLS technology is to forward packets based on a short and fixed length identifier termed as a “label” rather than the layer 3 IP addresses of the packets. The labels are assigned to each packet at the ingress node known as the Label Edge Router (LER) of an MPLS Domain.
MPLS routers make forwarding decisions based on the fixed length labels. The labels are detached as packets depart an MPLS domain at the egress LER. Within the MPLS domain, packets are forwarded using these labels by-the core Label Switch Routers (LSRs). The IP packets are switched through pre-established Label Switched Paths (LSP) by signaling protocols. LSPs are determined at the ingress LER and are unidirectional (from ingress to egress). Packets with the identical label follow the same LSP and are categorized into a single Forwarding Equivalence Class (FEC). An FEC can be defined as a group of IP packets, which are forwarded in the same manner along the same LSP.
A main point of interest with FECs in a traffic engineering context is that they support aggregation. All packets from different sources but entering the MPLS domain through the same LER, and bound to the same egress LER can be assigned to the same FEC and therefore the same virtual circuit. In other words, there is no need to establish a new virtual circuit for each (source, destination) pair read in the headers of incoming packets. Once ingress LER has determined the FEC of a packet, the ingress LER assigns a virtual circuit to the packet via a label number. Also, FEC definitions can take into consideration IP packet sources in addition to destinations. Two packets that enter the MPLS domain through the same LER and going to the same destination can use different sets of links so as to achieve load balancing, that is, put the same amount of traffic on all links thereby distributing the load of traffic on each link.
Traffic engineering deals with the performance of a network in supporting users' QoS needs. Traffic engineering for MPLS networks involves the measurement and the control of traffic. The objectives of traffic engineering in the MPLS environment are related to two performance functions:                1. Traffic oriented performance which includes QoS operations.        2. Resource oriented performance objectives which deal with networking resources to contribute to the realization of traffic oriented objectives.        
The aim of traffic engineering is to find mechanisms to satisfy the growing need of users for bandwidth; thus, the efficient management of the available bandwidth is the essence of traffic engineering. MPLS plays an important role in engineering the network to provide efficient services to its customers. The advantages of MPLS for traffic engineering include:                1. Label switches are not limited to conventional IP forwarding by conventional IP based routing protocols.        2. Traffic trunks can be mapped onto label switched paths.        3. Attributes can be associated with traffic trunks.        4. MPLS permits address aggregation and disaggregation (IP forwarding permits only aggregation)        5. Constraint-based routing is easy to implement.        6. MPLS hardware is less expensive than ATM hardware.Proper traffic engineering techniques are the basis of providing good QoS support to MPLS networks.        
Three main factors determine the performance of any network application, namely the supporting system, network and the protocol. Considering the architectural philosophy of IP, it imposes a restriction in that it does not support a fixed data flow model upon the network's application set. It does not take into consideration the “type” of traffic to route. It merely routes the traffic based on simple routing algorithms (mostly shortest path). In such cases, delay sensitive traffic can have an impact due to excessive injection of delay insensitive traffic because all types of traffic follow the same shortest path. This can be a drawback for multimedia traffic due to its time stringent nature. Another disadvantage of conventional IP routing is the amount of processing the core routers have to perform in order to forward a packet to its destination. In L3 (IP) routing, the network does not maintain state, the data packets following the first packet in a flow are unaware of its routing. Hence the route is calculated independently for every packet although they have the same destination address. MPLS improves these shortcomings in IP routing by combining L3 routing with L2 switching. It uses the first data packet to establish the LSP, and distributes a label to the FEC that the first data packet belongs to. If the data packets following the first one belong to the same FEC as the first data packet, then MPLS uses the same label to encapsulate them. Forwarding decisions are made on the basis of the fixed length short labels rather than the variable length IP header and longest prefix matches. This considerably reduces the processing time and in turn increases the core network's packet forwarding performance.
FIG. 1 shows the MPLS Shim Header. This header contains the actual label that is inserted between the layers 2 and 3 headers. The header is 32 bits long. It is worth noting here that the 3 experimental bits are marked as EXP. These bits are used to map the DiffServ Code point (DSCP) from the IP packet to the MPLS header to maintain QoS in a DiffServ MPLS environment.
These EXP bits are used to map certain information encoded within the multimedia packets onto the MPLS header so that the MPLS router has ample information and can decide on the basis of this information whether to discard a packet at times of congestion or not.